Tesi sul tema "Fire resist"
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1
Joseph, Rebecca Janine. "A fire in their bellies California teachers strategically and effectively resist a mandated reading curriculum /". Diss., Restricted to subscribing institutions, 2005. http://proquest.umi.com/pqdweb?did=888842011&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
2
Maloney, Margaret E. "A Trial of Fire and Ice: Assessing the Ability of Invasive Tree Pyrus Calleryana to Resist Disturbance During Grassland Invasion in The American Midwest". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1618854700620354.
3
Doumert, Bertrand. "Apport de la RMN 1D/2D à l'étude de systèmes inorganiques boratés : caractérisation structurale du réseau vitreux borophosphate et réactivité des retardateurs de flamme APP-ZBH". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2023/2023ULILR067.pdf.
Abstract (sommario):
La spectroscopie par Résonance Magnétique Nucléaire (RMN) à l'état solide est devenue une technique incontournable pour caractériser les matériaux inorganiques oxydes. Ces dernières années, la résolution des spectres RMN a été significativement améliorée par le développement de spectromètres de plus en plus puissants. Dans le contexte Lillois, cette amélioration de la résolution a particulièrement bénéficié aux études sur les matériaux boratés synthétisés par les différentes équipes de recherche de l'université. L'objectif de cette thèse est de soutenir le développement des études par RMN sur les matériaux boratés préparés localement en montrant notamment les apports des techniques de RMN de corrélation. Deux types de matériaux ont ainsi été sélectionnés pour l'étude : les verres de borophosphate de zinc préparés au LASIRE et les systèmes retardateurs de flamme à base de borate de zinc hydraté et de polyphosphate d'ammonium préparés à l'UMET.Les matériaux vitreux étudiés sont des borophosphates de zinc de composition xB2O3 - (50-x/2)ZnO - (50-x/2)P2O5, connus pour leur faible température de transition vitreuse (Tg) et leur bonne durabilité chimique. Les analyses par spectroscopie RMN avancée 11B et 31P 1D/2D ont permis de relier l'effet de formateur mixte observé sur la Tg avec la structure du réseau vitreux.Les systèmes de retardateur de flamme basés sur le borate de zinc hydraté (ZBH) et le polyphosphate d'ammonium (APP) sont couramment utilisés dans l'industrie. Les analyse par RMN 1D/2D de ce travail ont contribué à la compréhension du mécanisme de dégradation thermique de chaque composé dans un premier temps et à la compréhension de la réactivité entre les deux composés dans un second tempsSolid-state Nuclear Magnetic Resonance (NMR) spectroscopy has become an essential technique for characterizing inorganic oxide materials. In recent years, the resolution of NMR spectra has been significantly improved by the development of increasingly powerful spectrometers. In the Lille context, this improvement in resolution has particularly benefited studies on borate materials synthesized by the university's various research teams. The aim of this thesis is to support the development of NMR studies on locally-prepared borate materials, in particular by demonstrating the benefits of correlation NMR techniques. Two types of materials have been selected for study: zinc borophosphate glasses prepared at LASIRE, and flame-retardant systems based on hydrated zinc borate and ammonium polyphosphate prepared at UMET.The glassy materials studied are zinc borophosphates with the composition xB2O3 - (50-x/2)ZnO - (50-x/2)P2O5, known for their low glass transition temperature (Tg) and good chemical durability. Analyses by 11B and 31P 1D/2D advanced NMR spectroscopy linked the mixed-former effect observed on Tg with the structure of the glassy network.Flame retardant systems based on hydrated zinc borate (ZBH) and ammonium polyphosphate (APP) are commonly used in industry. The 1D/2D NMR analyses in this work have contributed to understanding the thermal degradation mechanism of each compound in the first instance, and to understanding the reactivity between the two compounds in the second
4
Berens, Sara Kathleen. "Residu(e/al)". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276704090.
5
Farhat, Ali Farag. "Basic problems of fibre-reinforced structural components when fibres resist bending". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/31095/.
Abstract (sommario):
This thesis generates certain sets of analytical and approximate solutions to a new class of partial differential equations stemming from a version of asymmetricstress elasticity theory appropriate for the study and prediction of the behaviour of fibre-reinforced materials containing fibres that resist bending. These new solutions are of theoretical and practical interest in the static and dynamic analysis of thinwalled, linearly elastic fibre-reinforced structures influenced by couple-stress and unsymmetric stress due to fibre bending stiffness. The static and free vibration solutions are constructed considering bending resistance fibres in a small deformation of beams and plates. Numerical results for displacements, stresses, couple-stress and natural frequencies of vibration are provided to investigate the influence of the fibres resistance in bending on the deformed beams and plates.
6
Orlicka, Dominika. "Development of novel coatings to resist fireside corrosion in biomass-fired power plants". Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/11825.
Abstract (sommario):
The emission of CO2 to the atmosphere from firing conventional fossil fuels has become a major concern for the power industry, due to the enhanced greenhouse effect and global warming predictions. The increasing worldwide demand for electricity production is another issue. The replacement of fossil fuels with increasing quantities of biomass is of interest as biomass is considered to be carbon neutral and is widely distributed. Unfortunately, due to its composition, the risk of fireside corrosion found on heat exchangers (super- heaters and re-heaters) is greater than in coal-fired plants. Consequently, biomass-fired power plants operate at lower steam temperatures and pressures, leading to their poorer efficiency. Biomass-fired power plants suffer from alkali chloride-induced corrosion, considered faster and more severe than alkali sulphate-based corrosion common in traditional coal-fired plants. The main aim of this project was to develop a range of novel coating compositions which would be resistant to fireside corrosion found on boiler tubes in biomass-fired power plants. To accomplish this, studies were carried out into salt stabilities, coating oxidation and deposit corrosion. Salt stability experiments have resulted in improved understanding of the evaporation and sulphidation behaviour of KCl, NaCl, K2SO4 and Na2SO4 at high temperatures in environments containing HCl and SO2. KCl was chosen as a deposit for coating screening. Two-target magnetron co-sputtering was successfully used to deposit a range of coating compositions. These coatings were analysed at 550°C in corrosion environments containing combinations of HCl, KCl and water vapour. The addition of gaseous HCl did not have a significant influence on the coating degradation compared to similar tests in air. Deposited KCl significantly increased the corrosion rate, whereas adding 10% moisture to the environment with KCl had little additional effect. The growth of either protective Cr2O3 or less protective mixed oxides was observed on the different coating compositions. The best performing coatings had compositions in the range: 26.2 – 79.4 at% Cr, 12.1 – 62.9 at% Fe, 8.5 – 10.9 at% Al.
7
Mahmoudzadeh, H. "Flow and orientation in fibre-loaded resins". Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637979.
Abstract (sommario):
The present work has successfully used an ingenious experimental technique to make a detailed examination of flow fields and fibre orientation patterns in a number of geometries. The experimental technique consisted of dispersing short glass fibres in mixtures of epoxy resins with matching refractive indices to that of the glass fibre. This made the glass fibres to 'disappear' in the mixtures and resulted in transparent mixtures. Light-reflective nickel particles and opaque tracer fibres were added to the mixture in order to investigate velocity fields and fibre orientation patterns. Experiments have covered concentrated, semi-concentrated, and (almost) dilute regimes. It has demonstrated a number of phenomena in flow-induced fibre orientation particularly in the concentrated region which have not been described before, and which should be taken into account in any predictive theories of fibre suspension flow and orientation. In the highly-concentrated suspensions, where C > (d/21), plug-flow type velocity fields exist. (Here C is the mixture concentration, d is the fibre diameter, and 21 is the fibre length). The fibre resin mixtures behave as non-homogeneous continua where fibre clumps are separated by resin-rich areas. These clumps apparently deform under shear, but seem capable of elastic recovery, facilitated by shear-induced clump rotation. In the semi-concentrated regime, where (d/21)2 < C < (d/21), expected degrees of alignment are diminished by fibre-fibre interactions. In this concentration regime and in some flow situations there is some evidence of rate dependence of alignments achieved, i.e. dependence on viscous stress levels. In the (almost) dilute regime, where C is just higher than (d/21)2, the fibre behaviour is in theory predictable from single fibre mechanics if the flow fields are of the linear type. However, in practice this is seldom the case. For this reason a theory has been developed and implemented in a computer program, which predicts fibre motion in arbitrary velocity fields.
8
Al-Obad, Zoalfokkar. "Designing PU resins for fibre composite applications". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/designing-pu-resins-for-fibre-composite-applications(561553ad-7bf1-4507-891a-00743c776637).html.
Abstract (sommario):
This thesis focuses on designing thermoplastic composites with high mechanical properties and a low processing temperature. Thermoplastic composites, which are used in this work, are composed of thermoplastic polyurethane (TPU) matrices and plain woven E-glass fabrics (GFs). TPUs were synthesised with large quantities of hard segments (HS), including 70% and 90%wt HS. The GF-TPU composites manufactured in this study have a melting point of around 175oC. As such, 180oC represents the processing temperature, which was used to produce GF-TPU composites. The influences of HS content and annealing treatment at 80oC on the thermal, dynamic mechanical and mechanical properties of TPU samples and GF-TPU composites with 25% fibre volume fraction (Vf) have been investigated. The highest crystallinity, storage modulus, Tg, yield strength, tensile strength and tensile modulus of all the TPU samples are seen in the TPU/90 samples annealed for 4 days. The TPU/90 samples display higher tensile properties than the TPU/70 and polypropylene (PP) samples, while the PP samples show the greatest elongation at break point. Furthermore, the tensile properties of the TPU/70 and TPU/90 samples are much higher than those of commercial TPUs. As such, annealed GF-TPU/90 composites with 25% Vf present the greatest dynamic mechanical, flexural, and tensile properties. GF-TPU/90 composites with 25% Vf show higher flexural strength than GF-PP composites or GF-polyamide 6 (PA6) composites with the same Vf. The effects of fibre surface treatments on the mechanical properties of GF and GF-TPU/70 composites with 25% Vf have also been studied in this investigation. GF treated with burn-off treatment is found to exhibit the lowest tensile properties. The interfacial adhesion between GF treated by NaOH for 0.5hrs and a TPU/70 matrix is greater than between GF treated by acetone for 5hrs and a TPU/70 matrix. Silanised GF presents greater tensile properties than desized GF. Thus, enhanced interfacial adhesion and tensile, flexural, ILSS and GIC properties are observed in the silanised GF-TPU/70 composites than in the desized GF-TPU/70 composites. GF-TPU/70 composites based on GFs treated by NaOH for 0.5hrs then sized with 0.15%wt. aminosilane display the greatest interfacial adhesion, flexural properties, ILSS and GIC, damage tolerance and impact-damage resistance. Conversely, the lowest interfacial adhesion, GIC, damage tolerance and impact-damage resistance are seen in the GF-PP composites based on 25% Vf as-received GF. There is a significant increase in the tensile and flexural properties of GF-TPU/90 composites with increasing the Vf from 25% to 50%. Moreover, the flexural strength of GF-TPU/90 composites with 50% Vf is not only higher than that of GF-EP composites or GF-vinyl ester composites with normalised 50% Vf, but is also much higher than that of GF-PP composites with 50% Vf. Despite this result, GF-TPU/90 composites with 50% Vf show the lowest fracture toughness, impact-damage resistance and damage tolerance, which are improved by adding 25% and 50%wt. of TPU/70 to the TPU/90 matrix. GF-TPU/90 composites based on a modified matrix have higher GIC, GIIC, impact-damage resistance and damage tolerance than GF-TPU/90 composites based on an unmodified matrix. The GIC, GIIC, impact-damage resistance and damage tolerance of GF-TPU/90 composites based on a modified matrix increase with increasing the percentage of TPU/70. Hence, the highest GIC, GIIC, impact-damage resistance and damage tolerance are seen in the GF-TPU/90 composites based on a modified matrix with 50%wt. of TPU/70.
9
Chaplin, Adam. "Novel matrix resins and composites". Thesis, University of Surrey, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259908.
10
Dhillon, Jagminder. "Coated fibre composites using rubbery and ductile fibre/matrix interlayers". Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/33043.
Abstract (sommario):
Advanced composite materials possessing high specific stiffness and strength have been successfully employed as structural materials in the aerospace, military and automotive industries. Despite the advantages that composites have over other materials, further development has been restricted by their brittleness. The aim of this research project was to improve the energy absorbing capabilities of unidirectional glass fibre epoxy resin composites by coating the fibres with an interlayer. UHMWPE was used as the interlayer because of its outstanding toughness while EPDM of low modulus was used to assess the difference between energy absorption through plastic deformations (UHMWPE) and highly elastic deformations (EPDM).
11
Beaumont, Sean. "The synthesis and evaluation of inherently fire retardant/low smoke unsaturated polyester resins". Thesis, Kingston University, 1997. http://eprints.kingston.ac.uk/20603/.
Abstract (sommario):
A study has been undertaken to attempt to overcome three major problems associated with common unsaturated polyester resins. These problems are the emissions of free styrene, high flammability and the emission of thick black smoke during combustion. A novel cross-linking monomer, containing two allyloxy substituents and one diethylamino substituent, has' been synthesised and purified in a two stage reaction using cyanuric chloride as the starting material. This new monomer contains five nitrogen atoms in an attempt to reduce smoke evolution and has a low volatility to reduce volatile organic emissions. It was found that this monomer was totally miscible with all resin types, based on both aromatic and aliphatic alkyds, and produced a degree of cross-linking in excess of 95% when cured with dicumyl peroxide at 90°C for 16 hrs and then 140°C for 3 hours. Combustion tests showed that the new resins produced considerably less smoke than the styrenated resins, show higher LOI values, i.e. require a higher percentage of oxygen to sustain combustion, and a lower surface spread of flame. These improved combustion properties are a direct result of the improved charring characteristics of the resins caused by the incorporation of the triazine monomer. It has been shown, however, that normal fire retardant phosphorus additives used in unsaturated polyester resins (UPRs) have little or no effect in the triazine resins and do not show any synergism with the nitrogen atoms in the new monomer. As a result of this, at high additive loading levels, the combustion behaviour improvements shown by the triazine resins over the styrenated resins are drastically reduced. It has also been shown that the triazine resins have a very high burning rate. The lack of phosphorus activity in the triazine resins has been shown to be caused by these resins thermally decomposing at low temperatures where the phosphorus is not active. This low decomposition temperature also leads to rapid decomposition and thus a high burning rate. The lack of synergism might be caused by the tertiary amine substituent being too stable towards interaction with the phosphorus additives; a primary amine might be more suitable. Mechanical studies have shown the new resin to be brittle in comparison to the styrenated resins but that it has increased Barcol hardness values, heat distortion temperature and flexural modulus.
12
Bott, Caroline Frances. "Water transport in epoxy resins and carbon-fibre composites". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46679.
13
Powell, Graham. "In-situ cure monitoring of epoxy resins systems". Thesis, Brunel University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242971.
14
King, David Gareth. "Fibre-optic sensor development for process monitoring of epoxy resins". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8698/.
Abstract (sommario):
An investigation was undertaken to examine the performance of a Fresnel reflection sensor (FRS) incorporated into a differential scanning calorimeter (DSC) to track the cross-linking of epoxy resins. The initial design used a micrometer translation stage to lower the FRS through an orifice in the DSC platinum lid and onto the pan containing the sample. During exothermic cross-linking experiments, the resin refractive index and the heat evolved were measured simultaneously, allowing for direct comparison between the data. Combining the two measurement techniques produced a powerful hyphenated analytical procedure that demonstrated the feasibility of using the FRS for in-situ cure monitoring of epoxy resin systems. During the cross-linking of specified resins, the sensor revealed optical phenomena throughout the latter stages and was shown to be sensitive to the glass transition temperature, nano-particulate movement, nano-particulate concentration and phase separation. Therefore, the introduction of the FRS to the DSC provided valuable cross-linking information. A second modification to the DSC permitted the accommodation of an optical fibre probe, which facilitated simultaneous DSC/FRS/Fourier transform infrared spectroscopy (FTIRS) analysis. Good correlation between the cross-linking kinetics of an epoxy resin system was demonstrated using the hyphenated techniques and hence alleviated the issues of cross-correlation between individual experiments.
15
Thanomsilp, Chuleeporn. "Toughening composites for liquid composite moulding". Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390838.
16
Aziz, Roslan Abd. "The influence of thermohumid conditions on compression-after-impact properties of fibre-reinforced laminate materials". Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/34052.
Abstract (sommario):
Advance composite materials based mainly on epoxy resins are being used in increasing amounts in aerospace components due to their high strength:weight ratio. Such components have to survive in a range of temperature and humid environments in different parts of the world. The current generation of epoxy resins used in high performance fibre reinforced laminates absorb moisture from the atmosphere. Moisture absorption by the epoxy resins leads to a reduction in glass transition temperature and to a softening of the resin with a loss of resin stiffness and strength. In certain applications the components have to survive low impacts from dropped tools and rough handling during maintenance. Low energy impacts of this nature are considered potentially dangerous mainly because the damage might be left undetected. Even where no visible impact damage is observed at the surface, matrix cracking and interlaminar failure can occur, and the load carrying properties of the composite components is considerably reduced. A compression after impact (CAI) test is widely used in industry as the major screening parameters for materials selection. The aim of the work reported in this thesis was to determine the influence of thermohumid conditions on CAI properties and to assess the degradation behaviour of composite laminates under these thermohumid conditions.
17
Xie, Xuying. "Marketing Analysis and Business Evaluation - : Marketing for a new firm Resort Västra Lägern". Thesis, Jönköping University, JIBS, EMM (Entrepreneurship, Marketing, Management), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-1194.
Abstract (sommario):
Hospitality, tourism and leisure are industry sectors where different factors impinge together
to provide a unique marketing context. The importance of concept intangibles, their
significance to life-style and cultural preferences of customers in themselves represent a
major challenge. Such intangibles may be more vulnerable to changes in customer perception
than the physical aspects of product and service delivery. However, intangibles also
present an opportunity for individual entrepreneurs to create alternative and differentiated
concepts, based on their own view and intuition of what customers will find appealing.
Resort Västra Lägern was founded under the circumstances. It is one new, small resort firm
in the countryside of Sweden. The owner identified the niche market in this traditional industry.
The favorable natural and cultural resources create the business background while
the active entrepreneurship makes the possibilities. At the start-up of the firm, marketing
analysis is necessary for this SME to position itself properly on the markets and to target
the customers effectively.
Marketing is absolutely central to the entrepreneurial process. For a new venture to be viable,
customers have to desire what it is being offered, in sufficient numbers, and prepared
to pay an economical price. This is at the heart of the marketing concept. However, an entrepreneurial
approach implies taking advantage of market opportunities in a dynamic, proactive
way.
18
Barran, Christopher David. "The effect of sizing resins on the interfacial adhesion of carbon fibre composites". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266154.
19
Korkees, Feras. "Modelling of water absorption into carbon fibre/epoxy composites". Thesis, Swansea University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678568.
20
Källner, Emelie. "Entrepreneurship Post Displacement:Exploring Knowledge Spillovers and Idea Generationas a Result of Business Closure". Thesis, KTH, Entreprenörskap och Innovation, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189562.
Abstract (sommario):
Empirical findings on knowledge transfers associated with business closures are limited (Hoetkerand Agarwal, 2007), and very few studies examine the search process of individuals and theirsearch for new solutions and ideas (Maggitti et al., 2013). The purpose of this paper is to fill theknowledge gap of knowledge spillovers and idea generation taking place while displacedemployees transition to entrepreneurship after business closure. This paper will examineAstraZeneca’s displaced employees that started their own businesses after AstraZeneca’sresearch and development facilities closed down in Lund (2010) and Södertälje (2012) inSweden. The research questions investigated were: What are the different factors and ideaprocesses that made the displaced employees start their own businesses? To what extent are theentrepreneurs utilizing their knowledge and experience gained at AstraZeneca in their currentbusinesses, and are they using contacts gained while working for AstraZeneca? To answer thesequestions both qualitative and quantitative research method were used in the form of surveys andinterviews. The results of this study showed that a knowledge spillover took place between thenew firms and the closing firm, while previous experience and expertise gained fromAstraZeneca greatly influenced the idea generation that took place amongst the displacedemployees while transitioning into entrepreneurship. Moreover, about 20% of theentrepreneurship was necessity based, whereas 70% were opportunity based. In regards to thetiming of the idea generation process, half of the participants came up with the business ideaafter learning about the closure, while the rest disagreed. Therefore, the idea generation processamongst the participants did not necessary start after the announcement of the displacement.
21
Xiao, Keqin. "Fracture behaviour of rubber-modified epoxies and their carbon fibre-reinforced composites". Thesis, The University of Sydney, 2000. https://hdl.handle.net/2123/27762.
22
Lebrão, Guilherme Wolf. "Estudo da viabilidade de fabricação de um tubo para construção de uma prótese de membro inferior em composito híbrido epóxi carbono-vidro". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-25062007-163320/.
Abstract (sommario):
Neste trabalho propôs-se a construção de um tubo de material compósito híbrido, com fibra de vidro e fibra de carbono, para utilização como prolongador de prótese de membro inferior a serem fabricadas pela AACD - Associação de Assistência à Criança Deficiente. O objetivo é avaliar as solicitações da prótese para otimizar custo e reduzir a massa. Fez-se inicialmente um levantamento das propriedades dos materiais comerciais utilizados para a fabricação do prolongador para referenciar o desenvolvimento do componente da prótese. Utilizou-se modelagem por elementos finitos para otimizar o componente em função dos esforços biomecânicos a que a prótese é submetida. Nesta modelagem, estudaram-se várias disposições, quantidade e material das camadas de forma a atender às solicitações e minimizar os custos. O levantamento bibliográfico permitiu encontrar uma rota de menor custo para a fabricação de compósito que utiliza um processo de transferência de resina auxiliado a vácuo e pré-formados de vidro e carbono. Como referência, foi fabricado um componente pelo processo de bobinagem filamentar que produz materiais compósitos de qualidade reconhecida. O processo de moldagem por transferência de resina assistido à vácuo, apesar de ter alguns insumos importados, pela sua simplicidade pode ser realizado na própria AACD e se mostrou capaz de obter componentes com custo que viabiliza sua produção sem grandes investimentos em equipamentos. Apesar da redução de algumas das propriedades em relação à peça de referência, o tubo apresentou vantagens na redução de massa e na absorção de impacto.In this work it was considered a construction of a pipe of hybrid composite material, with carbon and glass fibre, for use as prosthesis extension of inferior member to be manufactured for the Associação de Assistência à Criança Deficiente AACD. The objective is to evaluate the requests of prosthesis to optimize cost and to reduce weight. A survey of the properties of the commercial materials commonly used for the manufacture extension became initially a reference to the development of the final component. A finite element modeling was used to optimize the component in the biomechanics function related to the efforts which the prosthesis is submitted. In this modeling some disposals and numbers of layers, amount and material have been studied to take care of the requests and to minimize the cost. A bibliographical survey allowed finding a shipper route for the manufacture of composite that uses a process of vacuum assisted resin transfer molding and preforms of glass with carbon. As reference, a component was produced using filament winding process to compare the quality of the obtained composite pipe. The process, although to have some imported feed-stock, can be proper carried out by AACD and if it showed capable to produce components with cost that makes possible its production internally. Despite the reduction of some of the properties in relation to the reference part, the component presented advantages such as weight reduction and the impact absorption.
23
Zanini, Riccardo. "Studio dell’adenina come indurente per resine epossidiche e produzione di materiali compositi da fonti rinnovabili". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19235/.
Abstract (sommario):
A causa di una maggiore preoccupazione ambientale, la ricerca si sta muovendo verso lo sviluppo di nuovi prodotti bio-based. Il progetto è stato incentrato sulla possibilità di produrre materiali compositi utilizzando un sistema resina-indurente interamente ottenuto da fonti rinnovabili con fibre naturali totalmente green e sintetiche. In particolare, è stata studiata la possibilità di utilizzare l’adenina, una molecola atossica e derivante da fonte rinnovabile, per la produzione di compositi con fibre di lino, juta, carbonio vergine e riciclato con resina epossidica da fonte bio. In particolare è stato ottimizzato il ciclo di cura e sono state caratterizzate le proprietà termiche e meccaniche dei materiali prodotti mediante analisi DSC (Differential Scanning Calorimetry), DMA (Dynamic Mechanical Analysis) e TGA (Termo-Gravimetric-Analysis). Per comprendere meglio la reticolazione delle resine epossidiche, si è studiato il meccanismo di reazione tra l’adenina e un precursore epossidico attraverso spettroscopia 1H-NMR (Nuclear Magnetic Resonance).
24
Blohm, Maren Elizabeth Veatch. "Genetic and Environmental Effects on Growth, Resin and Rubber Production in Guayule (Parthenium Argentatum, Gray)". Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1329%5F1%5Fm.pdf&type=application/pdf.
25
Lenzi, Luca. "Valutazione dell’adenina come indurente da fonte rinnovabile per resine epossidiche commerciali e per la produzione di materiali compositi". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19228/.
Abstract (sommario):
Le resine più utilizzate industrialmente per la produzione di materiali compositi sono quelle epossidiche a base di diglicidil etere del bisfenolo A. Tipicamente, a livello industriale vengono utilizzate diammine sintetizzate da precursori tossici per l’ambiente e per l’uomo. Prendendo atto dell’intrinseca pericolosità di questi sistemi, sono state valutate delle alternative per rendere il processo di produzione dei materiali compositi più sostenibile e sensibile verso l’ambiente e la salute degli operatori. Questo progetto di tesi di laurea sperimentale è il proseguimento di un lavoro precedentemente svolto dal gruppo di ricerca che ha individuato l’adenina come un’alternativa non tossica e bio-based agli attuali agenti reticolanti. Nel presente lavoro di tesi, sono stati effettuati studi di formulazione e reticolazione dell’adenina con resine epossidiche commerciali da infusione e da impregnazione già utilizzate a livello industriale. L’obbiettivò è stato quello di ottenere formulati di resina e adenina capaci di dare un prodotto completamente reticolato, utilizzabile commercialmente e con elevati valori di Tg. Le formulazioni più promettenti così ottenute per ogni tipo di resina sono state utilizzate insieme a fibre di carbonio (vergini e riciclate), fibre di lino e di juta per la produzione di materiali compositi a fibra corta. Le formulazioni di resina e i compositi ottenuti sono stati caratterizzati mediante Analisi Termogravimetrica (TGA), Calorimetria Differenziale a Scansione (DSC) e Analisi Dinamico Meccanica (DMA).
26
Zhang, Xiangping. "Characterization of filament wound GRP pipes under lateral quasi-static and low velocity impact loads". Thesis, University of Aberdeen, 1998. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU551705.
Abstract (sommario):
Glass-fibre reinforced plastic pipes are widely used to convey fluids for various purposes. They offer a number of distinct advantages over conventional metals, such as high specific strengths, high specific moduli, superior corrosion resistance and low coefficient of thermal expansion. However, their behaviour under lateral quasi-static and impact loading are still not well known. The research programme described in this thesis was designed to characterise the performance of 55° winding angle GRP pipes, subjected to lateral quasi-static and impact loading. Two approaches: experimental tests and finite element analysis, were used to investigate the behaviour of the GRP pipes. The experimental investigation was started with diametral compression of short GRP pipes to examine the structural behaviour and failure mechanisms. Subsequently, lateral indentation tests were conducted on rigid-foundation supported or simply supported specimens using two different indenter geometries: line-ended and flat-ended. Furthermore, low-velocity impact tests were performed under similar conditions as those for indentation tests in order to characterise the response of the GRP pipes and to identify the correlation between the two forms of loading. The pipes exhibited multi-mode failure mechanisms, resin cracks, delaminations and fibre breakage. It is found that delamination, which resulted in significant loss in stiffness and strength, was the most significant mode of failure for the GRP pipes. A good correlation in behaviour was identified between quasi-static indentation and its energy equivalent low-velocity impact when the global bending stiffness of the GRP specimens were high. Specimens with span S 10.5D i, where Di is the internal diameter of the pipe, are considered to have high bending stiffness, while simply supported specimens with S10.5D i have low bending stiffness. Irrespective of the support conditions and loading type, specimens with high bending stiffness followed a failure mechanism sequence: local resin failure, delamination and the fibre breakage. However, the large global bending experienced by low bending stiffness specimens resulted in a change of failure mechanism, only local damage and surface tensile cracks were observed.
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Holanda, Elis?ngela Bezerra das Neves. "Morfologia e propriedades mec?nicas da fibra de sisal unidirecional e em sobreposi??o de comp?sito com resina ep?xi". Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15708.
Abstract (sommario):
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Previous issue date: 2013-01-14Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The composites manufactured with long fibres aligned in a single direction, and overlay has been shown to have better performance than the short fibers randomly distributed. In particular, the lignocellulosic fibers extracted from the sisal leaves, used in conjunction with the epoxy resin has attracted the attention of many researchers because the final properties of the system formed. In this work composites based on epoxy resin reinforced with sisal fibers were manufactured. The sisal fibres were treated with an alkaline solution of 0.06 mol/l NaOH. The treated, and untreated fibres were subjected to tension x extension tests. The composites were manufactured in the "Lossy" mold with the specifications of the samples to be produced (300x20x4 mm). The tension tests were carried out in accordance with the ASTM standards 3039 (for the composite aligned in a single direction) and ASTM D5573 (for composites in overlay), three point bending tests were performed according to ASTM D790. Analyzing the results of the tests of tension and three point bending tests, it was observed that the composites with the configuration of overlapping had the better elastic module in both tests. As to the maximum resistance to tension, the best result was the composites aligned in a single direction. Tests of absorption of water and micrographs are in progress
Os comp?sitos fabricados com fibras longas alinhadas unidirecionalmente e em sobreposi??o tem demonstrado que possuem melhor desempenho do que as fibras cortadas aleatoriamente distribu?das. Em especial, as fibras lignocelul?sicas extra?das do sisal, utilizadas em conjunto com a resina ep?xi tem atra?do a aten??o de muitos pesquisadores devido ?s propriedades finais do sistema formado. No presente trabalho foram fabricados comp?sitos ? base de resina ep?xi refor?ado com fibras de sisal. As fibras de sisal foram submetidas ao tratamento alcalino com NaOH a 0,06 mol/l, em seguida submetidas ao ensaio de tra??o na fibra tratada e n?o tratada. Os comp?sitos foram fabricados no molde denominado de Lossy (molde com perdas) usinado de acordo com as especifica??es das amostras a serem produzidas (300x20x4 mm). Os ensaios de tra??o foram realizados de acordo com as normas ASTM 3039 (Para os comp?sitos alinhados unidirecionalmente) e ASTM D5573 (Para os comp?sitos em sobreposi??o), os ensaios de flex?o em tr?s pontos foram realizados de acordo com as normas ASTM D 790. Analisando os resultados dos ensaios de tra??o e flex?o em tr?s pontos, foram observados que os comp?sitos com a configura??o de sobreposi??o teve melhor m?dulo de elasticidade em ambos os ensaios. Quanto a resist?ncia m?xima a tra??o o melhor resultado foi do comp?sito alinhado unidirecionalmente. No ensaio de absor??o de ?gua foi observado que os comp?sitos possuem um n?vel muito baixo de absor??o e o comp?sito alinhado unidirecionalmente obteve percentual de satura??o de 1,97 %. Nas micrografias, se observa as regi?es de ruptura/trincas do comp?sito e seu comportamento (fibra/matriz)
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Toure, Saran Mariam. "Manufacture and characterisation of carbon fibre prepreg stacks containing resin rich and resin starved slip layers". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/manufacture-and-characterisation-of-carbon-fibre-prepreg-stacks-containing-resin-rich-and-resin-starved-slip-layers(371ac2a8-b127-4137-813f-4c5d1b31627a).html.
Abstract (sommario):
The cost of manufacturing high quality composite components can be significantly reduced by using Out of Autoclave (OOA) processes if they can achieve final parts with a finish quality as high as that obtained using an autoclave process. Much research has been carried out recognising that regardless of the reinforcement fibre orientation, manufacturing of preimpregnated (prepregs) carbon components is much affected during its forming stage by fibre deformation and failure modes. This work sought to reduce wrinkling in the moulding of prepregs by introducing slip layers within the lay-up. Three types of slip layers were used: a dry fabric, a resin rich layer and a resin film. In order for the slip layers to be fully incorporated into the final laminate the resin content within the slip layer must be adjusted prior to crosslinking. In the case of dry fabric layer, additional resin must be introduced and in the case of a resin rich layer and resin film layer, excess resin has to be removed. The laminates used in the project were based on 2/2 twill and unidirectional carbon prepregs. These were manufactured by either Resin Infusion (RI) or Vacuum Bagging (VB). Resin adjustments were made at the same time. The 2/2 twill and unidirectional carbon prepregs were first characterised by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Thermal Analysis (DMTA) before RI and VB. Dry 2/2 twill and unidirectional carbon fabrics and/or Resin Film (for VB) or fabrics and Epoxy Resin (for RI) were introduced in several plybooks and then cured. Final parts were either made of 2/2 twill carbon or unidirectional carbon. The parts were used to investigate the relationship between individual plies during the consolidation of a plybook. The first characterisations were done on flat laminates. Also two moulds were manufactured and used to produce new parts for further characterisations. The first, an aluminium mould was machined using a Computer Numerical Control (CNC). The second mould was a fan blade, made using chopped strand mats. The final parts had 3, 4 or 6 plies. These parts were characterised using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Torsion testing. The results provide a first step towards understanding how the friction at a ply/ply level can be influenced by the "starving" or the "enriching" of resin in a plybook during its consolidation. The work showed that in OOA manufacturing, the friction at a ply/ply level can be controlled by introducing Resin Film, Dry or Resin Rich Fabrics in a prepreg plybook. It was demonstrated that introducing lubrication to control ply friction during forming can result in quality part as high as that obtained from a traditional composite forming process. As the final parts were made using a fixed die mould and a vacuum bag, most of the plies in the layups could deform individually and accommodate interply shear. Torsion testing on a number of a random selection of samples showed negligible effects on shear stresses, strengths and modulus within the parts were negligible. It is argued that the flexibility of the vacuum bag could have had an impact on the layups during forming. The plies could conform to the mould easier. This work has potential for other applications. For example in match die moulding, introducing wet lubrication could improve interply shear during forming and help in improving accuracy and geometrical conformity of final parts. Furthermore, developing techniques to control friction during forming in OOA can be attractive to industries which could not afford to invest in this OOA prepreg technology. OOA processing times have become very attractive to industries such as the sporting good, automotive, wind energy and transportation. These industries could explore the opportunity presented by the work in this EngD thesis.
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Liu, Yan. "Nano-reinforced epoxy resin for carbon fibre fabric composites". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/nanoreinforced-epoxy-resin-for-carbon-fibre-fabric-composites(284f8361-2530-4fc8-8abe-759ff2e57891).html.
Abstract (sommario):
This thesis reports a study of the effects on processing and properties of incorporating nano-scale reinforcements (multiwall carbon nanotubes, MWCNTs) in the matrix of epoxy- carbon fibre (CF) laminate composites to produce multi-scale composites (M-SC). The main aim of this research was to study the effects of MWCNTs on matrix toughening and the through-thickness properties of M-SCs based on a commonly used aerospace grade epoxy resin — triglycidyl-p-aminophenol (TGPAP) cured with diaminodiphenyl sulphone (DDS). In order to improve resin processing, diglycidyl ether of bisphenol F (DGEBF) was added into the TGPAP/DDS system as a reactive diluent. Factorial experimental design (FED) was used to optimize the composition of this tri-component system to obtain high Tg and low resin viscosity, which gave a TGPAP/DGEBF/DDS system with 30.56 wt.% of DGEBF and a chemical stoichiometry of 0.5. Three types of MWCNTs were used; as-received (AR-), base-washed (BW-) and amine functionalized (NH2-). These were shear-mixed with both the bi- and tri-component systems using a 3-roll mill to produce nanocomposite matrices (NCM). The curing behaviour, dispersion state of MWCNTs in the resin and processability of NCMs were studied to decide upon the preparation method for the final M-SC. The fracture toughness (KIC) and the flexural properties of NCM were affected by both MWCNTs and the matrix type; thus KIC increased by up to 8 % in TGPAP/DDS NCM but decreased by 23% in TGPAP/DGEBF/DDS NCM with 0.5 wt.% AR-CNTs. The addition of both non-functionalized and functionalized MWCNTs increased the flexural modulus. The failure mechanism of NCMs was found to be dominated by the size and distribution of CNT aggregates and the behaviour of MWCNTs, both those dispersed in the matrix and in aggregates. The addition of functionalized MWCNTs increased the interfacial bonding between MWCNT and epoxy resin and thus improved the mechanical properties. All the NCM systems were taken forward to manufacture M-SC using a hybrid resin film infusion (RFI)/hot press process. The fibre volume fraction and the void content could be controlled at 43 ± 5 % for M-SC with TGPAP/DDS NCM and 60 ± 6 % for M-SC with TGPAP/DGEBF/DDS NCM. M-SCs were characterised using a range of tests, including flexural, interlaminar shear strength (ILSS), mode-II interlaminar fracture toughness (GIIC), low velocity impact and compression after impact (CAI). The most obvious improvement occurred for the M-SC with tri-component system with 0.5 wt.% CNTs, whereILSS increased by 16 % upon adding NH2-CNTs and GIIC increased significantly on addition of 0.5 wt.% AR-CNTs and NH2-CNTs, by 85% and 184% respectively. However the effect of MWCNTs on other properties was at best marginal. For example, for the M-SC with TGPAP/DDS, the flexural modulus and ILSS only increased by 4.1 % and 2.3 % with 0.5 wt.% AR-CNT.
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Humphreys, Matthew. "Development and structural investigation of monocoque fibre composite trusses". Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15898/1/Matthew_Humphreys_Thesis.pdf.
Abstract (sommario):
Fibre composite materials are gaining recognition in civil engineering applications as a viable alternative to traditional materials. Their migration from customary automotive, marine, aerospace and military industries into civil engineering has continued to gain momentum over the last three decades as new civil engineering applications develop. The use of fibre composite materials in civil engineering has now evolved from non-structural applications, such as handrails and cladding, into primary structural applications such as building frames, bridge decks and concrete reinforcement. However, there are issues which are slowing the use of fibre composite materials into civil engineering. Issues include high costs, difficulties in realising potential benefits, general lack of civil engineers' familiarity with the material and relatively little standardisation in the composites industry. For composites to truly offer a viable alternative to traditional construction materials in the civil engineering marketplace, it is essential that these issues be addressed. It is proposed that this situation could be improved by demonstrating that potential benefits offered by composites can be achieved with familiar civil engineering forms. These forms must be well suited to fibre composite materials and be able to produce safe and predictable civil engineering structures with existing structural engineering methods. Of the numerous structural forms currently being investigated for civil engineering applications, the truss form appears particularly well suited to fibre composites. The truss is a familiar structural engineering form which possesses certain characteristics that make it well suited to fibre composite materials. In this research a novel monocoque fibre composite truss concept was developed into a working structure and investigated using analytical and experimental methods. To the best of the author's knowledge the research presented in this thesis represents the first doctoral research into a structure of this type. This thesis therefore presents the details of the development of the monocoque fibre composite (MFC) truss concept into a working structure. The developed MFC truss was used as the basis for a detailed investigation of the structural behaviour of the MFC truss elements and the truss as a whole. The static structural behaviour of the principal MFC truss elements (tension members, compression members and joints) was investigated experimentally and analytically. Physical testing required the design and fabrication of a number of novel test rigs. Well established engineering principles were used along with complex finite element models to predict the behaviour of the tested truss elements and trusses. Results of the theoretical analysis were compared with experimental results to determine how accurately their static structural behaviour could be predicted. It was found that the static structural behaviour of all three principal truss elements could be accurately predicted with existing engineering methods and finite element analysis. The knowledge gained from the investigation of the principal truss elements was then used in an investigation of the structural behaviour of the MFC truss. Three full-scale MFC trusses were fabricated in the form of conventional Pratt, Howe and Warren trusses and tested to destruction. The investigation included detailed finite element modelling of the full-scale trusses and the results were compared to the full-scale test results. Results of the investigation demonstrated that the familiar Pratt, Howe and Warren truss forms could be successfully manufactured with locally available fibre composite materials and existing manufacturing technology. The static structural behaviour of these fibre composite truss forms was accurately predicted with well established engineering principles and finite element analysis. A successful marriage between fibre composite materials and a civil engineering structure has been achieved. Monocoque fibre composite trusses have been developed in the familiar Pratt, Howe and Warren truss forms. These structures possess characteristics that make them well suited to applications as primary load bearing structures.
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Humphreys, Matthew. "Development and Structural Investigation of Monocoque Fibre Composite Trusses". Queensland University of Technology, 2003. http://eprints.qut.edu.au/15898/.
Abstract (sommario):
Fibre composite materials are gaining recognition in civil engineering applications as a viable alternative to traditional materials. Their migration from customary automotive, marine, aerospace and military industries into civil engineering has continued to gain momentum over the last three decades as new civil engineering applications develop. The use of fibre composite materials in civil engineering has now evolved from non-structural applications, such as handrails and cladding, into primary structural applications such as building frames, bridge decks and concrete reinforcement. However, there are issues which are slowing the use of fibre composite materials into civil engineering. Issues include high costs, difficulties in realising potential benefits, general lack of civil engineers' familiarity with the material and relatively little standardisation in the composites industry. For composites to truly offer a viable alternative to traditional construction materials in the civil engineering marketplace, it is essential that these issues be addressed. It is proposed that this situation could be improved by demonstrating that potential benefits offered by composites can be achieved with familiar civil engineering forms. These forms must be well suited to fibre composite materials and be able to produce safe and predictable civil engineering structures with existing structural engineering methods. Of the numerous structural forms currently being investigated for civil engineering applications, the truss form appears particularly well suited to fibre composites. The truss is a familiar structural engineering form which possesses certain characteristics that make it well suited to fibre composite materials. In this research a novel monocoque fibre composite truss concept was developed into a working structure and investigated using analytical and experimental methods. To the best of the author's knowledge the research presented in this thesis represents the first doctoral research into a structure of this type. This thesis therefore presents the details of the development of the monocoque fibre composite (MFC) truss concept into a working structure. The developed MFC truss was used as the basis for a detailed investigation of the structural behaviour of the MFC truss elements and the truss as a whole. The static structural behaviour of the principal MFC truss elements (tension members, compression members and joints) was investigated experimentally and analytically. Physical testing required the design and fabrication of a number of novel test rigs. Well established engineering principles were used along with complex finite element models to predict the behaviour of the tested truss elements and trusses. Results of the theoretical analysis were compared with experimental results to determine how accurately their static structural behaviour could be predicted. It was found that the static structural behaviour of all three principal truss elements could be accurately predicted with existing engineering methods and finite element analysis. The knowledge gained from the investigation of the principal truss elements was then used in an investigation of the structural behaviour of the MFC truss. Three full-scale MFC trusses were fabricated in the form of conventional Pratt, Howe and Warren trusses and tested to destruction. The investigation included detailed finite element modelling of the full-scale trusses and the results were compared to the full-scale test results. Results of the investigation demonstrated that the familiar Pratt, Howe and Warren truss forms could be successfully manufactured with locally available fibre composite materials and existing manufacturing technology. The static structural behaviour of these fibre composite truss forms was accurately predicted with well established engineering principles and finite element analysis. A successful marriage between fibre composite materials and a civil engineering structure has been achieved. Monocoque fibre composite trusses have been developed in the familiar Pratt, Howe and Warren truss forms. These structures possess characteristics that make them well suited to applications as primary load bearing structures.
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Thiagarajan, C. "Smart characterisation of damage in carbon fibre reinforced composites under static and fatigue loading condition by means of electrical resistivity measurements". Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309660.
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Du, Rand Marlene. "The influence of powder liquid ratio on the flexural strength of fibre reinforced acrylic resin material". Thesis, Cape Peninsula University of Technology, 2007. http://hdl.handle.net/20.500.11838/1535.
Abstract (sommario):
Thesis (MTech (Dental Technology Discipline))--Cape Peninsula University of Technology, 2007Practitioners often modify the powder:liquid ratio of polymethyl methacrylate resins (PMMA) to improve the handling properties of the material for certain procedures or because of personal preferences. While it is known that this influences the mechanical properties of unreinforced resin materials, little is known about its effect on glass fibre reinforced PMMA resin.
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Kukadia, Umesh. "ROOM TEMPERATURE CURING OF BIO-BASED RESINS AND PREPARATION OF THEIR COMPOSITES". Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19028.
Abstract (sommario):
In today’s world the significance of bio-based materials are increasing rapidly because ofthe environmental concern. Material scientists are nowadays engaged in development ofsuch materials which have natural origin and degrade in its environment. Several workshave already been reported in area of thermoplastic biocomposites. However biocompositesbased on thermosets is comparatively new area of research. In this work biobasedcomposites have been developed from two different bio-based thermoset resins.The main objective of the work was room temperature curing of poly lactic acid basedresin (POLLIT™) and AESO, acrylated epoxidized soy-bean oil (TRIBEST®). These tworesin systems were impregnated with different natural fibre mats. Cure behavior wascharacterized by means of DSC (Differential Scanning Calorimeter) and results showsthat the resins have been cured at room temperature. The mechanical properties ofprepared composites were assessed by the means of flexural testing and charpy impacttesting. The viability of using these composites in structural applications are also beendiscussed.Uppsatsnivå: D
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Rathnayake-Arachchige, Dilshani. "Metallisation and structuring of low temperature Co-fired ceramic for micro and millimetre wave applications". Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19343.
Abstract (sommario):
The recent developments in Low Temperature Co-fired Ceramic (LTCC) as a substrate material enable it to be used in the micro and millimetre wave range providing low dissipation factors at high frequencies, good dielectric properties and a high degree of integration for further miniaturised devices. The most common metallisation method used in LTCC technology is screen printing with high cost noble metals such as silver and gold that are compatible with the high sintering temperatures (850°C). However, these techniques require high capital cost and maintenance cost. As the commercial world requires convenient and low cost process technologies for mass production, alternative metallisation methods should be considered. As a result, electroless copper plating of fired LTCC was mainly investigated in this research. The main goals of this project were to carry out electroless plating of fired LTCC with sufficient adhesion and to extend the process to metallise closed LTCC channel structures to manufacture Substrate Integrated Waveguide (SIW) components. The objectives were focused on electroless copper deposition on fired LTCC with improved adhesion. Electroless deposits on the Sn/Pd activated LTCC surface showed poor adhesion without any surface pre-treatments. Hence, chemical etching of fired LTCC was carried out using concentrated NaOH solution. NaOH pre-treatment of LTCC led to the formation of flake like structures on the LTCC surface. A number of surface and chemical analysis techniques and weight measurements were used to investigate the mechanism of the modification of the LTCC surface. The results showed that the flake like structures were dispersed in the LTCC material and a material model for the LTCC structure was proposed. SEM EDX elemental mapping showed that the flake like structure consisted of aluminium, calcium, boron and oxygen. Further experiments showed that both the concentration of NaOH and the immersion time affect the surface morphology and the roughness of fired LTCC. The measured Ra values were 0.6 μm for untreated LTCC and 1.1 μm for the LTCC sample treated with 4M NaOH for 270 minutes. Adhesion tests including peel test and scratch test were carried out to examine the adhesion strength of the deposited copper and both tests indicated that the NaOH pre-treatment led to an improvement, with the best results achieved for samples treated with 4M NaOH. A second aspect of the research focused on the selective metallisation of fired LTCC. Excimer laser machining was used to pattern a resist film laminated on the LTCC surface. This process also roughened the substrate and created channels that were characterised with respect to the laser operating parameters. After patterning the resist layer, samples were activated using Sn/Pd catalyst solution followed by the electroless copper deposition. Electroless copper was selectively deposited only on the patterned LTCC surface. Laser parameters clearly affected the copper plating rate. Even with a similar number of shots per area, the tracks machined with higher repetition rate showed relatively more machining depth as well as good plating conditions with low resistance values. The process was further implemented to realize a complete working circuit on fired LTCC. Passive components including a capacitor and an inductor were also fabricated on LTCC using the mask projection technique of the excimer laser system. This was successful for many designs, but when the separation between conductor lines dropped below 18 μm, electroless copper started to deposit on the areas between them. Finally, a method to deposit copper films on the internal walls of closed channel structures was developed. The method was first demonstrated by flowing electroless copper solutions through silane treated glass capillaries. A thin layer (approx. 60 nm) of electroless copper was deposited only on the internal walls of the glass capillaries. The flow rate of the electroless copper solution had to be maintained at a low level as the copper deposits tended to wash away with higher flow rates. The structures were tested for transmission losses and showed low (<10dB) transmission losses in the terahertz region of the electromagnetic spectrum. The process was further applied to deposit electroless copper on the internal walls of the LTCC closed channel structures to manufacture a LTCC Substrate Integrated Waveguide (SIW).
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Oliveira, Jos? Orlando de. "Comp?sito refor?ado com sisal para aplica??o na moda". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15680.
Abstract (sommario):
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Previous issue date: 2012-03-30The objective of this research is the fabrication of a composite reinforced with dyed sisal fiber and polyester matrix for application in the fields such as, fashion, clothing, interior textiles; fashion accessories are some of the examples. For the fabrication of the composite, the sisal fibers were subjected to processes such as: chemical treatment with sodium hydroxide (NaOH) in the removal of impurities; bleaching for removing the yellowish color of the natural fiber and dyeing with direct dyes to confer the colors blue, green and orange. The search for new technologies ecologically correct has become a major concern in recent decades. Studies show that composite polymer reinforced by natural fibers is suitable for a large number of applications, and its use is advantageous in terms of economic and ecological. The dyed fibers were cut to a length of 30 mm, is used in the confection of webs. For this purpose, a web preparer by immersion, developed in the Laboratory of Chemical Textile of UFRN. The composite sheets measuring 300 x 300 x3 mm were molded by compression, with unsaturated orthophthalic polyester as matrix, and the samples in sizes 150 x 25 x 3 mm were cut with the aid of a laser machine, to be subjected to traction and flexion. The mechanical properties of traction and flexion in three points were performed in the Laboratory of metal and mechanical tests of Materials Engineering of UFRN. The resulting samples from the tests were evaluated in scanning electron microscope (SEM) at CTGas RN. On the basis of the analysis of the results from the mechanical tests, it was observed that the composite had good mechanical behavior, both in traction as in flexion. Furthermore, it was observed that in the water absorption test, the samples had a different percentage among themselves, this occurred due to the variation of density found in the fibre webs. The images of the SEM showed the failures from the manufacturing process and the adhesion of fibre/matrix. When the samples were prepared with the dyed fibers to be applied in fashion, the results were positive, and it can be concluded that the main objective of this work was achieved
A busca por novas tecnologias ecologicamente corretas tem se tornado uma grande preocupa??o nas ?ltimas d?cadas. Estudos comprovam que comp?sitos polim?ricos refor?ados por fibras naturais s?o adequadas a um grande n?mero de aplica??es e seu uso ? vantajoso em termos econ?micos e ecol?gicos. O objetivo desta pesquisa ? a fabrica??o de um comp?sito refor?ado com fibra de sisal tingida e matriz de poli?ster para aplica??o na moda: vestu?rio, t?xteis lar, acess?rios de moda etc. Para o seu beneficiamento, as fibras de sisal foram submetidas aos diversos processos: tratamento qu?mico com hidr?xido de s?dio (NaOH) na retirada das impurezas; alvejamento para remo??o da cor amarelada natural da fibra e tingimento com corantes diretos para conferir as cores azul, verde e alaranjado. As fibras tingidas foram cortadas com comprimento de 30 mm e utilizadas na confec??o das mantas. Para isso utilizou-se um preparador de manta por imers?o, desenvolvido no Laborat?rio de Qu?mico T?xtil da UFRN. Os comp?sitos medindo 300 x 300 x 3 mm foram moldados por compress?o, com poli?ster insaturado ortoft?lico como matriz, e as amostras nos tamanhos 150 x25 x3 mm foram cortadas com aux?lio de uma m?quina ? laser, para serem submetidas ? an?lise mec?nica de tra??o e flex?o. As propriedades mec?nicas de tra??o e flex?o em tr?s pontos foram realizadas no Laborat?rio de Metais e Ensaios Mec?nicos de Engenharia de Materiais da UFRN. As amostras resultantes das propriedades mec?nicas foram avaliadas no Microscopio Eletronico de Varredura (MEV) no CTG?s RN. Com base nas an?lises dos resultados dos ensaios mec?nicos, observou-se que os compositos tiveram bom comportamento mec?nico, tanto na tra??o como na flex?o. Tamb?m observou-se que no ensaio de absor??o de ?gua, as amostras tiveram um percentual diferente entre si, isso ocorreu devido ? varia??o da densidade encontrada nas mantas. As imagens do MEV mostraram as falhas provenientes do processo de fabrica??o e a ades?o fibra/matriz. Quando foram preparadas as amostras com as fibras tingidas para serem aplicadas na moda, os resultados foram positivos e pode-se concluir que o objetivo principal do presente trabalho foi atingido
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Flores, Jose. "The Violin Concerto and the Second Symphony by Johannes Brahms: Musical Resemblance as a Result of the Proximity in their Dates of Composition". Diss., Tucson, Ariz. : University of Arizona, 2006. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1446%5F1%5Fm.pdf&type=application/pdf.
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Islam, Mohammad Saiful. "The Influence of Fibre Processing and Treatments on Hemp Fibre/Epoxy and Hemp Fibre/PLA Composites". The University of Waikato, 2008. http://hdl.handle.net/10289/2627.
Abstract (sommario):
In recent years, due to growing environmental awareness, considerable attention has been given to the development and production of natural fibre reinforced polymer (both thermoset and thermoplastic) composites. The main objective of this study was to reinforce epoxy and polylactic acid (PLA) with hemp fibre to produce improved composites by optimising the fibre treatment methods, composite processing methods, and fibre/matrix interfacial bonding. An investigation was conducted to obtain a suitable fibre alkali treatment method to: (i) remove non-cellulosic fibre components such as lignin (sensitive to ultra violet (UV) radiation) and hemicelluloses (sensitive to moisture) to improve long term composites stability (ii) roughen fibre surface to obtain mechanical interlocking with matrices (iii)expose cellulose hydroxyl groups to obtain hydrogen and covalent bonding with matrices (iv) separate the fibres from their fibre bundles to make the fibre surface available for bonding with matrices (v) retain tensile strength by keeping fibre damage to a minimum level and (vi) increase crystalline cellulose by better packing of cellulose chains to enhance the thermal stability of the fibres. An empirical model was developed for fibre tensile strength (TS) obtained with different treatment conditions (different sodium hydroxide (NaOH) and sodium sulphite (Na2SO3) concentrations, treatment temperatures, and digestion times) by a partial factorial design. Upon analysis of the alkali fibre treatments by single fibre tensile testing (SFTT), scanning electron microscopy (SEM), zeta potential measurements, differential thermal analysis/thermogravimetric analysis (DTA/TGA), wide angle X-ray diffraction (WAXRD), lignin analysis and Fourier transform infrared (FTIR) spectroscopy, a treatment consisting of 5 wt% NaOH and 2 wt% Na2SO3 concentrations, with a treatment temperature of 120oC and a digestion time of 60 minutes, was found to give the best combination of the required properties. This alkali treatment produced fibres with an average TS and Young's modulus (YM) of 463 MPa and 33 GPa respectively. The fibres obtained with the optimised alkali treatment were further treated with acetic anhydride and phenyltrimethoxy silane. However, acetylated and silane treated fibres were not found to give overall performance improvement. Cure kinetics of the neat epoxy (NE) and 40 wt% untreated fibre/epoxy (UTFE) composites were studied and it was found that the addition of fibres into epoxy resin increased the reaction rate and decreased the curing time. An increase in the nucleophilic activity of the amine groups in the presence of fibres is believed to have increased the reaction rate of the fibre/epoxy resin system and hence reduced the activation energies compared to NE. The highest interfacial shear strength (IFSS) value for alkali treated fibre/epoxy (ATFE) samples was 5.2 MPa which was larger than the highest value of 2.7 MPa for UTFE samples supporting that there was a stronger interface between alkali treated fibre and epoxy resin. The best fibre/epoxy bonding was found for an epoxy to curing agent ratio of 1:1 (E1C1) followed by epoxy to curing agent ratios of 1:1.2 (E1C1.2), 1: 0.8 (E1C0.8), and finally for 1:0.6 (E1C0.6). Long and short fibre reinforced epoxy composites were produced with various processing conditions using vacuum bag and compression moulding. A 65 wt% untreated long fibre/epoxy (UTLFE) composite produced by compression moulding at 70oC with a TS of 165 MPa, YM of 17 GPa, flexural strength of 180 MPa, flexural modulus of 10.1 GPa, impact energy (IE) of 14.5 kJ/m2, and fracture toughness (KIc) of 5 MPa.m1/2 was found to be the best in contrast to the trend of increased IFSS for ATFE samples. This is considered to be due to stress concentration as a result of increased fibre/fibre contact with the increased fibre content in the ATFE composites compared to the UTFE composites. Hygrothermal ageing of 65 wt% untreated and alkali treated long and short fibre/epoxy composites (produced by curing at 70oC) showed that long fibre/epoxy composites were more resistant than short fibre/epoxy composites and ATFE composites were more resistant than UTFE composites towards hygrothermal ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, fracture toughness, SEM, TGA, and WAXRD test results. Accelerated ageing of 65 wt% UTLFE and alkali treated long fibre/epoxy (ATLFE) composites (produced by curing at 70oC) showed that ATLFE composites were more resistant than UTLFE composites towards hygrothermal ageing environments as revealed from tensile, flexural, impact, KIc, SEM, TGA, WAXRD, FTIR test results. IFSS obtained with untreated fibre/PLA (UFPLA) and alkali treated fibre/PLA (ATPLA) samples showed that ATPLA samples had greater IFSS than that of UFPLA samples. The increase in the formation of hydrogen bonding and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased IFSS for ATPLA system compared to UFPLA system. Long and short fibre reinforced PLA composites were also produced with various processing conditions using compression moulding. A 32 wt% alkali treated long fibre PLA composite produced by film stacking with a TS of 83 MPa, YM of 11 GPa, flexural strength of 143 MPa, flexural modulus of 6.5 GPa, IE of 9 kJ/m2, and KIc of 3 MPa.m1/2 was found to be the best. This could be due to the better bonding of the alkali treated fibres with PLA. The mechanical properties of this composite have been found to be the best compared to the available literature. Hygrothermal and accelerated ageing of 32 wt% untreated and alkali treated long fibre/PLA composites ATPLA composites were more resistant than UFPLA composites towards hygrothermal and accelerated ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, KIc, SEM, differential scanning calorimetry (DSC), WAXRD, and FTIR results. Increased potential hydrogen bond formation and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased resistance of the ATPLA composites. Based on the present study, it can be said that the performance of natural fibre composites largely depend on fibre properties (e.g. length and orientation), matrix properties (e.g. cure kinetics and crystallinity), fibre treatment and processing methods, and composite processing methods.
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SALMON, LAURENT. "Etude de la degradation hydrolytique de l'interface fibre-matrice dans les materiaux composites fibres de verre-resine epoxyde". Paris, ENSAM, 1997. http://www.theses.fr/1997ENAM0019.
Abstract (sommario):
Un reseau multicouches d'organosilane est depose sur la surface des fibres de verre, des leur fabrication, pour promouvoir et maintenir l'adhesion entre le verre et la matrice organique du composite. Afin d'etudier la cinetique de vieillissement de ce reseau, nous avons synthetise, a partir d'organosilanes couramment utilises avec le systeme fibre de verre-resine epoxyde, des materiaux modeles macroscopiques. Nous avons caracterise ces modeles et etudie leur vieillissement dans diverses conditions d'humidite relative et de temperature. Nous avons pu montrer que les reseaux modeles pouvaient vieillir soit par hydrolyse des liaisons chimiques qui lient les molecules d'organosilane (liaisons siloxane) soit au contraire par une augmentation du degre de condensation des materiaux. Nous avons explique ces evolutions contradictoires a l'aide d'un modele cinetique. Nous avons enfin tente de correler les resultats obtenus a partir des modeles avec ceux obtenus lors du vieillissement de composites resine epoxyde-fibre de verre, differant par la nature chimique de l'agent de couplage utilise lors de l'ensimage des fibres.
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Jacques, Didier. "Transfert de charge entre fibre et matrice dans les composites carbone-resine : comportement en traction d'un modèle monofilamentaire". Vandoeuvre-les-Nancy, INPL, 1989. http://www.theses.fr/1989NAN10324.
Abstract (sommario):
Le transfert de charge entre fibre et matrice dans les composites carbone-resine a été étudié à travers le comportement en traction d'un composite modèle à monofilament. Cet essai de fragmentation a été adapté aux résines de type fragile utilisées dans l'industrie aérospatiale. Les résultats mettent en évidence la sensibilité du paramètre ainsi obtenu à toute modification du système (état de surface de la fibre, nature de la matrice, humidité. . . ). Un dispositif expérimental de traction sous microscope a été réalisé pour étudier la cinétique de l'essai de fragmentation et en particulier, les micromécanismes interagissant à l'interface. Parallèlement, une modélisation du processus de fragmentation a permis d'expliquer les résultats expérimentaux et de révéler l'influence des paramètres du système. Une extension aux composites a été proposée, démontrant que la capacité de transfert de charge peut être utile pour l'interprétation et l'optimisation des propriétés des composites
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Stuhlinger, Martin Ernst. "The influence of mixing ratio on the fatigue behaviour of fibre reinforced polymers". University of the Western Cape, 2013. http://hdl.handle.net/11394/5041.
Abstract (sommario):
Magister Scientiae Dentium - MSc(Dent)Statement of the problem: Fibre reinforcement of polymethyl methacrylate (PMMA) denture base material is known to improve the strength, as well as the fatigue behavior, of the material. The powder liquid (P/L) ratio of PMMA is often changed to modify the handling properties of the material. Little is known about the effect of this deviation from manufacturer’s guidelines on the fatigue behaviour of the fibre reinforced product. Purpose: This study compared the flexural strength (FS) of PMMA reinforced with glass fibre using different P/L ratios, before and after cyclic loading. Methods and materials: Three groups, with 50 glass fibre reinforced (everStick nonimpregnated fibers) heat-cured PMMA resin (Vertex Rapid Simplified) specimens each, were prepared using a custom-made template (dimensions 10x9x50mm). Each group had a different P/L ratio: the control group (100%) had the manufacturer’s recommended ratio; the 90% and 80% groups had reduced P/L ratios (by weight).Twenty five specimens from each group were subjected to a 3-point bending compression test using a universal testing machine. The remaining 25 specimens from each group were subjected to cyclic loading (104 cycles) before compression testing. The (FS) was calculated using the highest force (Fmax) before specimen failure. Flexural strength was calculated using the equation: FS=3WL/2bd2. Within each group, median FS values before and after cyclic loading were compared by means of a non-parametric analysis of variance. The Aligned Ranks Transform method was used for the analysis. Statistical significance was set at p=0.05. Results: The Fmax (N) of the control (100%), 90% and 80% groups fatigued and unfatigued were 100%: 1665 (fat), 1465 (unfat); 90%: 1679 (fat), 1548 (unfat) and 80%: 1585 (fat), 1467 (unfit) respectively. There was no significant interaction between Mix ratio and Fatigue state, and the 80% mix had a significantly higher mean than either the 90% or 100% mix (with differences of about 0.3 units for both). The Fatigued state had a higher mean than the Un- fatigued state by about 6.0 units. Using FS (MPa) it was found that the fatigued 80% mix specimens had the highest value. The FS MPa of the control (100%), 90% and 80% groups fatigued and un-fatigued were 64.3, 60.6; 66.9, 65.6 and 70.2, 69.3 respectively. The fact that fatiguing strengthened the specimens merits further research. When observing the broken specimens it was found that there was a complete debonding of the fibres and the PMMA. Conclusion and clinical relevance: a) Fibre: The benefit of using glass fibre bundles to reinforce prostheses fabricated using heat cured PMMA is questionable due to problems with bonding between the fibre bundles and the heat cured PMMA resin. b) Fatiguing: An average person chews 107 times during a 3 year period. A limited period of average masticatory forces should not have a detrimental effect on prostheses made from heat cured PMMA resin. c) Mix ratio: Within the normal parameters of laboratory techniques the mix ratio of PMMA resin had no significance on the fracture resistance of the prostheses. Due to the high cost of the fibres used for the reinforcement and the limited success and insignificant results achieved in this study, this researcher cannot recommend using Stickbond or Stick fibers for the reinforcement of dentures made with heat cured PMMA resin.
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Ribeiro, Luciene Mendes. "Estudo da flamabilidade e resist?ncia ? chama de comp?sito de poli?ster insaturado e fibra da folha do abacaxizeiro (PALF)". Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15662.
Abstract (sommario):
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Previous issue date: 2011-08-11In the present research work, composites were prepared using pine apple leaf fibres (PALF) as reinforcement with unsaturated polyester resin as matrix, incorporating with fire retardant at different compositions. The PALF was obtained from the decortication of pine apple leaves obtained from Ramada 4 from Ielmo Marinho in the State of Rio Grande do Norte. The unsaturated polyester resin and the catalyzer were bought from the local establishment. The fire retardant, aluminium tri-hydroxide - Al(OH)3 was donated by Alcoa Alum?nio S.A and was used in the proportions of 20%, 40% and 60% w/w. Initially the fibres were treated with 2% NaOH for 1 hour, to remove any impurities present on the fibre surface, such as wax, fat, pectin and pectate, in order to have a better adsorption of the fibres with the matrix as well as the flame retardant. The fibre mat was prepared in a mat preparator by immersion, developed in the Textile Engineering Laboratory, at the UFRN. The composites (300x300x3 mm) were prepared by compression molding and the samples (150x25x3 mm) for analysis of the properties were cut randomly using a laser cutter. Some of the cut samples were used to measure the smoke emission and fire resistance using UL94 standard. Mechanical tension-extension and flexural properties were carried in CTG?s RN and the Laborat?rio de Metais e Ensaios Mec?nicos Engenharia de Materiais UFRN , as well as SEM studies were carried out at N?cleo de Estudos em Petr?leo e G?s Natural - UFRN . From the observed results, it was noted that, there was no marked influence of the fire retardant on the mechanical properties. Also in the water absorption test, the quantity of water absorbed was less in the sample with higher concentration of fire retardant. It was also observed that the increase in the proportion of the fire retardant increased the time of burning, may be due to the compactness of the composite due to the presence of fire retardant as a filling material even though it was meant to reduce the rate of inflammability of the composite
Na presente pesquisa foram desenvolvidos comp?sitos com fibras da folha do abacaxizeiro (PALF - Pineapple Leaf Fiber), utilizando resina de poli?ster insaturado como matriz, incorporando retardante de chama em diferentes composi??es. As fibras da folha do abacaxizeiro foram obtidas na ramada 4 do munic?pio de Ielmo Marinho no Estado do Rio Grande do Norte. A resina de poli?ster insaturado e o catalisador foram comprados no com?rcio. O retardante de chama de alumina trihidratada (hidr?xido de alum?nio - Al(OH)3) foi doado pela empresa Alcoa Alum?nio S.A. e foi utilizado em propor??es de 20%, 40% e 60% do peso do material utilizado na fabrica??o dos comp?sitos. As PALFs foram tratadas com 2% de hidr?xido de s?dio, por 1 hora, para eliminar as impurezas superficiais tais como ceras, gorduras, pectinas e pectatos, para que houvesse uma melhor ades?o da matriz ?s fibras, bem como do retardante de chama. As mantas de fibras foram preparadas num preparador de manta por imers?o, desenvolvido no Laborat?rio de Engenharia T?xtil da UFRN. Os comp?sitos (300x300x3 mm) foram moldados por compress?o e as amostras (150x25x3 mm) para an?lise das propriedades foram cortadas, em diferentes posi??es da placa do comp?sito com aux?lio de uma m?quina de laser. As propriedades mec?nicas de tra??o e flex?o em tr?s pontos foram realizadas no CTG?s RN e no Laborat?rio de Metais e Ensaios Mec?nicos de Engenharia de Materiais da UFRN. Os testes da emiss?o de fuma?a e resist?ncia ao fogo foram realizados no Laborat?rio de Engenharia T?xtil da UFRN, utilizando a norma UL94. As amostras resultantes das propriedades mec?nicas foram avaliadas no MEV do N?cleo de Estudos em Petr?leo e G?s Natural da UFRN. Com base nas an?lises dos resultados nos ensaios mec?nicos, observou-se que o retardante de chama n?o tem influ?ncia significativa. Tamb?m observou-se que no ensaio de abosor??o de ?gua, quanto maior a concentra??o de retardante de chama, a quantidade de ?gua absorvida ? menor. No teste de inflamabilidade, observou-se que quanto maior a concentra??o de retardante de chama, maior o tempo de queima. Pode ser conclu?do que a presen?a de retardante de chama, al?m de atuar como inibidor de chama, tamb?m atua como uma carga que influ?ncia a compacta??o do comp?sito e desta forma reduz a taxa de queima
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Bettelli, Mercedes Amelia. "Effect of Induction-Heat Post-Curing on Residual Stresses in Fast-Curing Carbon Fibre Reinforced Composites". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80527.
Abstract (sommario):
Manufacturing induced shape distortions is a common problem for composite materials. Due to the non-isotropic nature of carbon fibre reinforced polymers (CFRP) unavoidable deformations occur during part production. During fabrication of polymer composites, the material obtains its final shape at elevated temperatures. The curing process involves a transition from the liquid state to the solid, glassy state, allowing bonding between fibres and matrix. As the material cools the mismatch in thermal expansion coefficients and cure shrinkage obtained during the matrix polymerization leads to residual stresses on the mechanical level within composite part. There is a great interest from the aircraft and automotive industries, to increase the ability to understand development of shape distortions and residual stresses during the cure, since these deformations often lead to dissatisfaction of tolerances and it is essential to predict the deformations beforehand in order to compensate time and cost. In this context, a study of residual stresses during the curing process of thermosetting resin composites is presented. A methodology is proposed for predicting the formation and development of manufacturing- induced residual stresses. The present project reports on a comprehensive experimental study on the dependency of different short curing cycles on the build-up of residual stresses in a carbon fibre/fast-curing epoxy system and evaluate of post-curing methods through induction heating and oven post-curing with unidirectional [904] and unsymmetrical [9020] laminates. It includes characterization in thermo-elastic properties and degree-of-cure of the material by Thermal bending test, thermal expansion test, mechanical tensile test and Differential Scanning Calorimetry (DSC) in non-post-cured and post-cured laminates. The results showed slight variation in the thermal properties and not effect in the mechanical properties at different cure and post-curing conditions. Analytical data by Laminate Analysis program validated the experimental thermo-elastic data with analytical simulations. In addition, it is shown improvements in the temperature distributions in the post-curing by induction heating with different experimental set-ups, however, oven post-curing showed a more systematic system, higher heat efficient a low cure temperature, with more consistent mechanisms of shape distortions and residual stresses compared to induction heating. These findings are relevant for the future development of prediction methods for process induced deformations of Fast Curing Epoxy Resins (FCER).
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Wang, Peng. "Étude numérique et expérimentale de procédé d’élaboration des matériaux composites par infusion de résine". Thesis, Saint-Etienne, EMSE, 2010. http://www.theses.fr/2010EMSE0568/document.
Abstract (sommario):
En aéronautique, l’élaboration via des pré-imprégnés n’est pas toujours adaptées àla fabrication de nouvelles pièces de formes complexes ou de grandes dimensions. Desprocédés directs existent, dénommés Liquid Composites Molding (LCM), tels que leResin Transfer Moulding (RTM) ou les procédés d’infusion de résine, comme le LiquidResin Infusion (LRI) et le Resin Film Infusion (RFI). Actuellement, environ 5 à 10%des pièces composites sont fabriqués par ces procédés directs. Avec le procédé RTM,les tolérances dimensionnelles et la porosité peuvent être maîtrisées et on peut atteindredes pièces haute qualité, mais son industrialisation est complexe et les modèlesmécaniques doivent être améliorés pour réaliser des simulations représentatives. Parcontre, les procédés d’infusion peuvent être utilisés dans des conditions plus flexibles,par exemple, dans des moules ouverts à sac vide en nylon ou silicone, à faible coût. Parconséquent, les procédés de LRI et RFI sont particulièrement adaptés pour les petites etmoyennes entreprises car les investissements sont plus faibles par rapport à d’autresprocédés de fabrication.Les procédés par infusion de résine LRI ou RFI sont basés sur l’écoulement d’unerésine liquide (pour RFI, après le cycle de température, la résine solide obtenir son étatliquide) à travers l’épaisseur d’un renfort fibreux sec dénommé préforme.L’optimisation du procédé est difficile à réaliser car le volume de la préforme changefortement pendant le procédé car elle est soumise à une pression extérieure et qu’il n’ya pas de contre-moule. Pour optimiser les paramètres de fabrication des matériauxcomposites par infusion de résine, il est nécessaire de mettre en oeuvre un modèlenumérique. Récemment, une modélisation de l'écoulement d’un fluide isotherme dansun milieu poreux compressible a été développée par P. Celle [1]. Avec ce modèlenumérique, nous avons simulé des cas test en 2D pour des géométries industriellesclassiques. Pour valider ce modèle numérique, des essais d’infusion d’une plaque par leprocédé LRI dans des conditions industrielles ont été réalisés. D’une part, la simulationnumérique permet de calculer le temps de remplissage, l’épaisseur de la préforme et lamasse de la résine durant l’infusion. D’autre part, nous avons suivi de procédéexpérimentalement par des micro-thermocouples, la fibre optique et la projection defranges. Un des points clefs de l’approche expérimentale est que l’écoulement de larésine et le comportement de la préforme dépendent intrinsèquement de paramètres quiévoluent pendant l’infusion de la résine, tels que la variation de l’épaisseur, le temps deremplissage et le taux volumique de fibres, via la perméabilité. Enfin, une comparaisonentre les résultats expérimentaux et la simulation numérique permet de valider lemodèle numérique. Cette confrontation des résultats permettra de mettre en lumière lesdifficultés et les limites de ce modèle numérique, afin d’améliorer les futurs modèles.De plus, ces deux approches constituent un bon moyen d’étudier et d’approfondir nosconnaissances sur les procédés d’infusion de résine, tout en développant un outil desimulation indispensable à la conception de pièces composites avancéesWeight saving is still a key issue for aerospace industry. For instance 50% in weightof the B787 and A350 aircraft structures is made of CFRP, so it is necessary to makelighter thick and complex parts. Direct processes called Liquid Composite Molding(LCM), such as Resin Transfer Moulding (RTM) or Resin Infusion Process (LRI, RFI).At the present time, around 5 to 10% of the parts are manufactured by direct processesand the current trend is clearly to go ahead. In RTM process, the dimensional tolerancesand porosity fraction can be kept under control and high quality parts produced, but itsindustrialisation is complex and refined models are still needed to perform simulations.On the contrary, the resin infusion process can be utilized in flexible conditions, such asin low cost open moulds with vacuum bags in nylon or silicone. This type of processonly requires low resin pressure and the tooling is less expensive than RTM rigidmoulds. Therefore LRI and RFI processes are particularity suitable for small andmedium size companies because the investments are rather low compared to othermanufacturing process.Liquid Resin Infusion (LRI) processes are promising manufacturing routes toproduce large, thick or complex structural parts. They are based on the resin flowinduced across its thickness by pressure applied onto a preform / resin stacking.However, both thickness and fibre volume fraction of the final piece are not wellcontrolled since they result from complex mechanisms which drive the transientmechanical equilibria leading to the final geometrical configuration. In order tooptimize both design and manufacturing parameters, but also to monitor the LRIprocess, an isothermal numerical model has been developed by P. Celle [1], whichdescribes the mechanical interaction between the deformations of the porous mediumand the resin flow during infusion. With this numerical model, we have investigated theLRI process with classical industrial piece shapes. To validate the numerical model andto improve the knowledge of the LRI process, the researcher work details a comparisonbetween numerical simulations and an experimental study of a plate infusion testcarried out by LRI process under industrial conditions. From the numerical prediction,the filling time, the resin mass and the thickness of the preform can be determined. Onanother hand, the resin flow and the preform response can be monitored bymicro-thermocouples, optical fibre sensor and fringe projection during the filling stage.One key issue of this research work is to highlight the major process parameterschanges during the resin infusion stage, such as the preform and resin temperature, thevariations of both thickness and fiber volume fraction of the preform. Moreover, thesetwo approaches are both good ways to explore and improve our knowledge on the resininfusion processes, and finally, to develop simulation tools for the design of advancedcomposite parts
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Hassler, Ulf. "Tomographie X bi-énergie de matériaux composites". Grenoble INPG, 1997. http://www.theses.fr/1997INPG0049.
Abstract (sommario):
La tomographie x bi-energie permet, sous certaines conditions, de reconstruire quantitativement la distribution spatiale de la masse volumique de deux materiaux de base. Nous appliquons cette technique au controle non-destructif de materiaux composites, afin d'obtenir une bonne separation des materiaux de la matrice et des fibres. Dans la premiere partie de cette these, nous presentons les principaux composants d'un systeme de tomographie ainsi que les interactions physiques qui y ont lieu. Nous effectuons une serie de simulations du processus d'acquisition pour determiner l'influence d'un certain nombre de parametres sur les images reconstruites. Afin de reduire le niveau de bruit eleve des densites reconstruites, nous proposons l'application d'une segmentation structurelle de l'objet suivie d'un filtrage selectif. Dans la deuxieme partie, nous etudions une methode de calibration independante de la composition et de la densite des materiaux examines. Cette methode est basee sur la modelisation et l'estimation des proprietes spectrales du systeme d'acquisition. Nous determinons, a partir de mesures de transmission d'un jeu d'objets d'etalonnage, le spectre du rayonnement emis par le tube x et l'efficacite du systeme de detection. Ces proprietes spectrales sont ensuite utilisees pour le calcul analytique des fonctions de separation de la matrice et des fibres. Les resultats experimentaux, obtenus sur un banc experimental de tomographie au cea-leti, montrent la validite de l'approche de calibration proposee. L'inspection de materiaux composites est appliquee sur un echantillon compose de resine d'epoxy avec des fibres de verre. Mots cles : tomographie x bi-energie, double-energie, calibration, estimation de spectres x, efficacite de detection, materiaux composites, controle non-destructif.
46
Terry, Shelley Rose. "Five Female Characters Driven to Suicide in Plays by 20th-Century Female Playwrights as a Result of Domestic Violence in a Patriarchal Society". University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279146596.
47
Triana, Cedeno Guillermo A. "Identification of possible human errors that can result in fires/explosions during tankers' cargo loading/unloading operations at the XYZ marine petroleum terminal". Online version, 2000. http://www.uwstout.edu/lib/thesis/2000/2000trianag.pdf.
48
Mazzotti, Riccardo. "Studio e caratterizzazione di materiali compositi a matrice polimerica e rinforzo in fibre naturali". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19453/.
Abstract (sommario):
I materiali compositi CFRP possiedono proprietà funzionali e di resistenza sempre più performanti grazie alla natura dei rinforzanti in fibra di carbonio, i quali però sono caratterizzati da criticità relative al processo di trasformazione, altamente energivoro e dispendioso, all’inquinamento collegato alla produzione delle fibre e al trattamento di sizing, nonché alla difficoltà nello stadio di separazione dei costituenti del manufatto composito e del conseguente riciclo.
A causa di queste problematiche sono stati introdotti in produzione materiali a matrice epossidica rinforzata con fibre di lino.
A seguito di un'introduzione su lavorazione e vantaggi delle fibre naturali, con particolare attenzione alle applicazioni in ambito compositi, sono discusse diverse prove di caratterizzazione meccanica e fisica di un composito a matrice polimerica e rinforzo in fibra naturale. Sono state eseguite delle prove di resistenza meccanica a trazione, taglio, compressione e ILSS per la determinazione delle proprietà meccaniche necessarie in fase di progettazione. Alcune prove meccaniche sono state effettuate su materiale saturo d'acqua, per ottenere informazioni sullo scadimento delle proprietà meccaniche indotto dall'assorbimento d'acqua e umidità. Sono inoltre state eseguite prove di igroscopicità per ottenere una panoramica precisa sulle differenze nella struttura delle fibre in carbonio e lino, che le differenzia in modo apprezzabile. Sono stati laminati compositi reticolati secondo tecnologia in autoclave, le cui proprietà fisiche sono state definite mediante prove alla fiamma al conocalorimetro, prove di igroscopicità del composito, prove ottiche al SEM in seguito ad una rottura in trazione.
49
Raimondo, Marialuigia. "Improving the aircraft safety by advanced structures and protecting nanofillers". Doctoral thesis, Universita degli studi di Salerno, 2014. http://hdl.handle.net/10556/1480.
Abstract (sommario):
2012 - 2013Inspection and Maintenance are important aspects when considering the availability of aircraft for revenue flights. Modern airframe design is exploiting new exciting developments in materials and structures to construct ever more efficient air vehicle able to enable efficient maintenance. The improvement in the aircraft safety by advanced structures and protecting nanofillers is a revolutionary approach that should lead to the creation of novel generation of multifunctional aircraft materials with strongly desired properties and design flexibilities. In recent years, the development of new nanostructured materials has enabled an evolving shift from single purpose materials to multifunctional systems that can provide greater value than the base materials alone; these materials possess attributes beyond the basic strength and stiffness that typically drive the science and engineering of the material for structural systems. Structural materials can be designed to have integrated electrical, electromagnetic, flame resistance, and possibly other functionalities that work in synergy to provide advantages that reach beyond that of the sum of the individual capabilities. Materials of this kind have tremendous potential to impact future structural performance by reducing size, weight, cost, power consumption and complexity while improving efficiency, safety and versatility. It is a well-known fact that, actually, also a very advanced design of an aircraft has to take required inspection intervals into account. An aircraft with inherent protective abilities could help to significantly extend the inspection intervals, thereby increasing aircraft availability. The challenge in this research is to develop and apply a multifunctional composite for structural applications. The aim of this project is the formulation, preparation and characterization of structural thermosetting composites containing dispersed protective nanofillers. This project specifically targets composites tailored for multifunctional applications such as lightning strike protection, and flame resistance. These composites were designed to enable their application on next generation aircrafts. With regard to the objectives of this PhD project the multifunctional composite systems were developed with the aim of overcoming the following drawbacks of the composite materials: • reduced electrical conductivity; • poor flame resistance. The thermosetting material was projected considering compatibility criteria so that to integrate different functions into a material that is capable of bearing mechanical loads and serves as a structural material element. [edited by author]
XII n.s.
50
Sakka, Aymen. "Investigation of Heat Conduction Through PMC Components Made Using Resin Transfer Moulding". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23508.
Abstract (sommario):
The increasing demand for polymer matrix composites (PMCs) from the airframe industry raises the issues of productivity, cost and reproducibility of manufactured PMC components. Performance reproducibility is closely related to the manufacturing technique. Resin transfer moulding (RTM) offers the advantage of flexible manufacturing of net-shape PMC components with superior repeatability starting from ready-to-impregnate dry reinforcements. An RTM apparatus was developed for manufacturing PMC plates and demonstrator components representative of actual, PMC components and PMC moulds made and used in the airframe industry. The RTM process developed in this work involved making net-shape dry carbon fibre preforms and impregnating them an epoxy resin, targeting mould applications. Thermal repeatability of different net-shape PMC components manufactured using the RTM apparatus developed in-house was investigated. Effects of bonding an outer copper plate onto the PMC material, targeting mould applications known as integrally heated copper tooling (IHCT), were explored. Heat conduction through the PMC components was studied using simulation models validated by experimental data obtained primarily by thermography. Manufactured PMC components showed good repeatability, particularly in terms of thermal behaviour. The IHCT technique was found to be well suited for mould applications. Expected advantages of thermography were materialised. Finally, the simulation models developed were in good agreement with experimental data.